1. Field of Invention
The present invention relates to a manufacturing method of a semiconductor structure.
2. Description of Related Art
In manufacturing an image sensor chip (e.g., a CMOS chip), a glass sheet is often used to cover a surface of a wafer for protecting the wafer from the attachment of dust to the image sensing area of the wafer. For a chip from dicing the wafer and used in an electronic product, a housing of the electronic product aligned with the chip usually has been disposed with a light transmissive that exhibits similar protection function to that of the glass sheet on the surface of the chip. Therefore, it is not only economically inefficient in the cost but also results in reduction to light transmittance.
However, for the surface of the wafer without the glass sheet, although the light transmittance may be improved and the image sensing capability of the chip from dicing the wafer is thus enhanced, the thickness of the wafer becomes so thin that it is very difficult to move the wafer along with ball grid arrays thereon.
Moreover, if the image sensing area is not protected by any elements in a manufacturing process of an image sensor, the image sensing area is vulnerable to dust pollution, which causes yield loss. For example, when the image sensor is fixed on a printed circuit board through a reflow oven, the image sensing area not covered by a glass sheet would be seriously polluted. Alternatively, the image sensor without a glass sheet needs to be manufactured in a high-grade clean room that increases manufacturing cost.